Generally, the widely-used peripheral input device of a computer system includes for example a mouse device, a keyboard device, a trackball device, or the like. Via the keyboard device, characters or symbols can be inputted into the computer system directly. As a consequence, most users and most manufacturers of input devices pay attention to the development of keyboard devices. The keyboard devices are classified into two types, i.e. the keyboard devices for desktop computers and the keyboard modules for notebook computers.
FIG. 1 is a schematic top view illustrating the outer appearance of a conventional keyboard module. As shown in FIG. 1, plural keys 10 are formed on a surface of the conventional keyboard module 1. These keys 10 are classified into several types, e.g. ordinary keys 101, numeric keys 102 and function keys 103. When one of these keys 10 is pressed by the user's finger, a corresponding signal is issued to the computer, and thus the computer executes a function corresponding to the pressed key. For example, when an ordinary key 101 is pressed, a corresponding English letter or symbol is inputted into the computer. When a numeric key 102 is pressed, a corresponding number is inputted into the computer. In addition, the function keys 103 (F1˜F12) can be programmed to provide various functions. The conventional keyboard module 1 is a keyboard device for a notebook computer.
Hereinafter, the inner structure of a conventional keyboard module will be illustrated in more details. FIG. 2 is a schematic cross-sectional view illustrating a conventional keyboard module. As shown in FIG. 2, the conventional keyboard module 2 comprises plural keys 20, a membrane switch circuit member 21 and a base plate 22. Each key 20 comprises a keycap 201, a scissors-type connecting element 202 and an elastic element 203. From top to bottom, the keycap 201, the scissors-type connecting element 202, the elastic element 203, the membrane switch circuit member 21 and the base plate 22 of the conventional keyboard module 2 are sequentially shown. The base plate 22 is used for supporting the keycaps 201, the scissors-type connecting elements 202, the elastic elements 203 and the membrane switch circuit member 21. For supporting these components, the base plate 22 is preferably made of a metallic material in order to provide the stronger structural strength. The conventional keyboard module 2 is a keyboard device for a notebook computer (not shown).
In the key 20, the keycap 201 is exposed outside the conventional luminous keyboard module 2, so that the keycap 201 can be pressed by the user. The scissors-type connecting element 202 is used for connecting the keycap 201 and the base plate 22. The elastic element 203 is penetrated through the scissors-type connecting element 202. In addition, both ends of the elastic element 203 are contacted with the keycap 201 and the membrane switch circuit member 21, respectively. The membrane switch circuit member 21 comprises an upper wiring plate 211, a spacer layer 212, and a lower wiring plate 213. The upper wiring plate 211 has plural upper contacts 2111. The spacer layer 212 is disposed under the upper wiring plate 211, and comprises plural perforations 2121 corresponding to the plural upper contacts 2111. The lower wiring plate 213 is disposed under the spacer layer 212, and comprises plural lower contacts 2131 corresponding to the plural upper contacts 2111. The plural lower contacts 2131 and the plural upper contacts 2111 are collectively defined as plural key switches 214. While the keycap 201 is pressed by the user, the keycap 201 is moved downwardly to push the elastic element 203 and trigger the corresponding key switch 214. During the triggering process, the movable distance of the keycap 201 in the downward direction is defined as a travelling distance.
Recently, the general trends in designing electronic devices (e.g., notebook computers or tablet computers) are toward slimness and light weightiness, and thus the conventional keyboard module needs to meet the requirements of slimness. For achieving this purpose, the manufacturers of the keyboard modules make efforts in minimizing the thickness of the keyboard modules. In accordance with the conventional approach, the thicknesses of the components of the keyboard module should be as small as possible. Nowadays, a keyboard module without the travelling distance was introduced into the market. The keyboard module is not equipped with the keycaps 201, the scissors-type connecting elements 202 and the elastic elements 203 as shown in FIG. 2. On the other hand, this keyboard module is equipped with a pressing layer in replace of the conventional keys 20. The pressing layer is a thin plastic film with plural key parts corresponding to the locations of the keycaps 201 as shown in FIG. 2. Moreover, symbols, letters or numbers are printed on the corresponding key parts. When one of the key parts is pressed, the membrane switch circuit member under the pressed key part is triggered to generate the corresponding key signal. In addition, the key part is subjected to slight deformation and not moved. Consequently, this keyboard module may be referred as the keyboard module without the travelling distance.
However, since the membrane switch circuit member only has a key switch corresponding to one key part. Since the key switch is located at a middle region of the key part, the user has to press the middle region of the key part in order to trigger the corresponding key switch. If the middle region of the key part is not pressed, the key signal is not generated. In other words, the conventional keyboard module is not user-friendly.
Therefore, there is a need of providing an improved slim-type keyboard module in order to overcome the above drawbacks.